1. Field of the Invention
The present invention relates in general to a method and apparatus for inspecting tubular members and, in particular, to an apparatus and method for inspecting tubular couplers and tubular member ends.
2. Brief Description of Related Art
Tubular members are often inspected by passing magnetic fields through the tubular member. Where a flaw is found in a wall of the tubular member, the magnetic field will deviate causing magnetic flux to leak from the surface of the tubular member. A suspension containing ferromagnetic particles visible to the human eye under appropriate conditions is sprayed on the tubular member while the tubular member rotates within the magnetic field. Deviation of the magnetic field and flux leakage cause a congregation of ferromagnetic particles disposed on the surface of the tubular member at the site of the deviation of the magnetic field. The location of the congregation may be marked to identify the flaw in the tubular member. This process may cause an undesirable residual magnetization of the tubular member.
When inspecting the end areas of tubular members or short coupler tubular members, the short length of the end or coupler may cause deviation of the magnetic field and end flux leakage that is unrelated to a flaw in the end or coupler. These deviations and end flux leakage will appear as tubular member flaws. Thus, a special apparatus is needed to closely control the passage of the magnetic field through the tubular member when inspecting the ends of a tubular member or a tubular coupler. These special apparatuses are adapted to inspect only the ends of a tubular member and are positioned in a manner that may cause the end portion of the tubular member to be pulled into contact with the apparatus when the magnetic field is passed through the tubular member. Therefore, there is a need for an inspection apparatus that inspects tubular member ends and couplers without leaving the tubular member magnetized and does not face the risk of damage caused by contact between the tubular member and the apparatus.